Hello.

I am writing this on behalf of a friend, he has a 996tt like myself, but non-X50, 420hp stock.

He bought the car about a year ago and he's been having this problem:

When the car accelerates, at first turbine pressure starts to rise as it should up to about 0.6-0.7, but then it immediately drops to 0.2-0.3 although gas pedal has not been released.
So the car does not accelerate as it should.

At first he had some faulty sensors: oil pressure sensor (oil pressure gauge falling to zero thing, turning on 'check engine' light), he replaced it. He also recently replaced intake pressure sensor (or whatever it's called), turbine bypasses and also the turbine pressure electric valve. Still the same problem. Everyone is clueless. No PIWIS errors.

If turbine pressure valve is forced open (mechanic somehow tweaked it as an experiment), pressure rises way above 1.0 and does not drop and the car accelerates like crazy. )))
So it looks like the ECU is somehow responsible for this... ECU is 100% stock.

Any ideas, please?

p.s. The car was imported from Arab Emirates.

 

Try a boost leak test.

 

if the n75 is disconnected from the motronic you have baseboost around 0,3 bar...maybe the electrical circuit is open to the n75 valve...but in this case your have a clear failure code in the motronic

check failure codes motronic and do a leak test...

 

There are no failure codes in the ECU. If the valve is blocked, the pressure goes up and does not drop, which clearly means there are no leaks. It's the ECU that opens the bypass valve once the pressure goes up.

 

So you're not willing to test for leaks?

 

Could be a bad BV. +1 for a boost leak test

 

Could be a bad BV. +1 for a boost leak test

 

could be a bad DV etc...

but you need to check the turbos.. make sure they are not damaged... then make sure the Wgs open up correctly ... and finally a pressure test...
all this can be done in 2 hours with less then $100 in parts...

 

Also could be a CAT has come out of it's seat and is blocking the exhaust. It happened to me and caused varying boost pressure problems. You have to take the muffler off to see it.

 

Thank you for comments, everyone, I'll post an update once we locate the problem. Thanks again.

 

What are the empty images that you included in your post? These:

Looks like this person is using the forum for SEO.

 

Spam...thanks for reporting it.